add formatting doc and pre-commit

CONTRIBUTING.md

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+# Contribution Guidelines
+
+## Code Formatting
+
+We format all Rust code using edition 2021 rules. This edition is defined in our Cargo.toml and most methods below will pick this up automatically.
+
+### Manual Method
+
+The most editor agnostic way to format your Rust code is by manually running cargo's fmt sub command.
+
+To check if your code is formatted without making changes, run `cargo fmt --check`. Then if you want to format your code you can run just `cargo fmt`.
+
+### VScode
+
+We recommend the meta extension Rust, which includes rust-analyzer. Then to set your editor to format on save:
+
+* In Visual Studio Code, press Control + Shift + P or Command + Shift + P (Mac) to open the command palette and type setting and then select Preferences: Open User Settings option.
+* Search for format on save setting and check the checkbox.
+
+You can also set language specific settings as outlined [here](https://code.visualstudio.com/docs/getstarted/settings#_language-specific-editor-settings). You will again want to then search for format on save and check the checkbox.
+
+### Other Editors
+
+You will first need to [install rust-analyzer](https://rust-analyzer.github.io/manual.html#installation), then configure your editor and install any needed plugins or extensions as outlined on that page.
+
+### Pre Commit Hook
+
+If you want to think about formatting your code less and just have git yell at you whe you try to commit code that is not properly formatted, you can use a simple pre-commit hook.
+
+After cloning the repo, the file `pre-commit-hook` to `.git/hooks/pre-commit`. That's it.

pre-commit

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+#!/bin/bash
+
+cargo fmt --check